1. Field of the Invention
Finishing chamber linings, finishing chambers lined therewith, various finishing machines comprising such lined finishing chambers, and method of making and using the same.
2. Prior Art
The art is replete with so-called finishing machines of various types, especially vibratory or gyratory types, with or without additional rotative action, or with rotative or centrifugal action alone, and of course tumbling barrels are a type of finishing machine which have been known for years. As the art has progressed, the finishing chambers employed have been lined with an elastomeric substrate of either natural or synthetic nature for prevention of damage to parts or workpieces being finished due to impingement thereof upon the inner surface of the finishing chamber during the process of finishing therein. Such finishing has generally been conducted in the finishing chamber of such finishing machines employing a suitable loose abrasive media and parts or workpieces to be finished, usually together with a liquid such as water, and frequently together with agents such as detergents, brightening agents, or lubricating agents of a soapy nature, generally referred to as "compounds". In the finishing chambers of such devices, the parts or workpieces to be finished are subjected to relative movement with respect to the loose finishing media, which may be anything from rock fragments to ceramic "chips" to steel burnishing balls, and the vibratory and/or rotative action imparted to the finishing chamber when in place in such finishing machines produces such relative motion. In vibrational or gyrational apparatus, such relative motion is considered to be both of a micro and a macro nature, inasmuch as the parts to be finished and the loose media move back and forth with respect to each other in an extremely localized area to an extremely localized extent in addition to moving with a generally rolling motion. In both tub-type and curvilinear finishing machines, having an arcuate bottom, the entire mass of loose finishing media and parts or workpieces generally moves with a rolling motion, going down at the inside of the finishing chamber and coming up at the outside of the finishing chamber, such motion generally being referred to as the "roll". In addition, in curvilinear finishing machine, e.g., the gyratory type of a machine having a curvilinear finishing chamber, usually an annular bowl having a U-shaped cross-section, with or without a step in the bottom, an additional component known as "feed" or "precession" is also introduced. According to the skill of the art, this is generally controlled by the relative settings of weights carried by an eccentric shaft or located on opposite ends of the shaft of an eccentric motor. Sometimes, in linear tub-type vibratory finishing machines, such precession is also provided by employing a corresponding slope in the bottom of the finishing chamber.
As the art has progressed, the elastomeric finishing chamber linings have become more and more sophisticated, as might be expected. However, they have not necessarily been satisfactory for all purposes, even at their previous highest degree of development. Efforts have been made to improve their compression-resilient properties and their wear-resistant properties. See, for example, U.S. Pat. No. 4,162,900, which is representative of finishing chamber linings of an improved nature. However, improved compression and wear-resistance are not the only problems inherent in such finishing chamber linings. In point of fact, a more important shortcoming of existing linings is only recognized and remedied according to the present invention, since prior thereto the problem, although recognized, was thought to be unidentifiable with any particular element of the finishing machine or chamber, and hence efforts to solve the said problem were not made by attention to and alteration of the finishing chamber lining.
The problem is as follows: Since introduction of vibratory finishing in the late 1950's, it has been difficult to make finishing media, particularly metal finishing media, and particularly steel balls as are used for burnishing and cleaning of parts, "roll" and "feed". In both tub-type and bowl-type vibratory machines, the mass of parts to be finished and finishing material would suddenly and unpredictably "flatten out" and refuse to "roll", thus not performing the intended function of the process and machine, inasmuch as vibratory finishing processes require a smooth, orbital, rolling action or "roll" to "scrub" the parts and keep them buried in the mass of finishing material. This problem worsened with the introduction of annular gyratory finishing machines of the SPIRATRON (TM - Roto-Finish Company, Inc.) type, because of the rise in the arcuate bottom of such devices. The finishing machine would suddenly stop "feeding", as this term has been above-defined. The problem was also aggravated by the introduction of synthetic elastomeric finishing chamber linings, such as polyurethanes, which have replaced the natural rubbers to a large extent. The reasons for the problem are unknown, but the problem in retrospect appears to be related to material hardness. In general, urethane linings are harder than rubber, and hence have been previously considered longer-wearing and more economical, but in retrospect it is believed that the hardness of the urethane linings contributes at least in part to the problem just outlined, which can be characterized as inactivity, depression, or dead spots within the finishing chamber when in use with finishing media and workpieces to be finished therein.
No prior art proposing or leading to a solution of the problem is known to the inventor, except as outlined hereinafter.
Many factors are considered to be involved in this erratic phenomenon or behavior of the finishing media and workpieces during the vibratory finishing process, among which are the size, the structure, the amplitude and frequency of the vibrations, the design of the machine, the type of workpieces involved, the type of loose finishing material and "compound" involved, possible eddying within the mass of media and workpieces caused by the design or shape of the finishing material, and so on. Many factors are obviously involved in this stagnation of the work action within the finishing chamber of a vibratory finishing machine when it occurs.
Temporarily stable conditions have sometimes been achieved by varying the following conditions:
1. Vibrator power. An increase in eccentric force is the most common method employed. This has the drawback of increased machine cost, low bearing life, hammering of the parts, a high noise level, and a higher media-wear rate.
2. Chemical "compound" variation. By varying the lubricity of the chemical "compound" employed, improved results can sometimes be obtained. This was probably the most significant prior technique but, for unknown reasons, cannot be relied upon. Considerable work is still being done in this area.
3. Varying machine speed of vibration. Here again, only a temporary cure is provided. Variable speed drives are, moreover, expensive.
4. Ribbing, scoring, or dimpling the finishing chamber lining. This approach is in wide use, but generally provides only a temporary cure for the stagnation phenomenon.
5. Feeding vanes. The addition of feeding vanes definitely interferes with parts and generally provides only a temporary solution.
6. Variation in drain size, type, and number of drains. This has some effect on the stagnation phenomenon, but not a major effect.
7. All of the foregoing. Variations of all of the foregoing are generally employed in difficult situations. Even so, some customer problems cannot be solved, resulting in return of a finishing machine or the loss of a sale since the machine simply cannot be made to perform satisfactorily under use conditions.
8. Addition of fine abrasives. The addition of fine abrasives, such as ten-micron silica, to the mass of finishing media and workpieces is effective in some cases to make the mass "roll" and "feed", but the abrasive discolors the media and parts and therefore is not acceptable. Even colloidal silica has been introduced into the mass with fair results as far as improvement of "feed" and "roll" phenomena, but still exhibits the disadvantage of discoloration of parts and media.
Accordingly, it is apparent that a solution to this longstanding problem is long overdue and highly desirable. Such is provided according to the present invention.